全文获取类型
收费全文 | 1742篇 |
免费 | 118篇 |
国内免费 | 1篇 |
出版年
2021年 | 12篇 |
2019年 | 15篇 |
2018年 | 24篇 |
2017年 | 20篇 |
2016年 | 27篇 |
2015年 | 41篇 |
2014年 | 49篇 |
2013年 | 104篇 |
2012年 | 84篇 |
2011年 | 82篇 |
2010年 | 43篇 |
2009年 | 39篇 |
2008年 | 86篇 |
2007年 | 87篇 |
2006年 | 94篇 |
2005年 | 81篇 |
2004年 | 95篇 |
2003年 | 80篇 |
2002年 | 104篇 |
2001年 | 44篇 |
2000年 | 49篇 |
1999年 | 53篇 |
1998年 | 21篇 |
1997年 | 21篇 |
1996年 | 17篇 |
1995年 | 16篇 |
1994年 | 28篇 |
1993年 | 22篇 |
1992年 | 41篇 |
1991年 | 39篇 |
1990年 | 31篇 |
1989年 | 38篇 |
1988年 | 30篇 |
1987年 | 19篇 |
1986年 | 25篇 |
1985年 | 23篇 |
1984年 | 23篇 |
1983年 | 12篇 |
1982年 | 8篇 |
1981年 | 17篇 |
1980年 | 10篇 |
1979年 | 11篇 |
1978年 | 9篇 |
1977年 | 9篇 |
1976年 | 7篇 |
1975年 | 8篇 |
1974年 | 8篇 |
1973年 | 12篇 |
1972年 | 9篇 |
1970年 | 9篇 |
排序方式: 共有1861条查询结果,搜索用时 31 毫秒
1.
Tobacco Genetic Tumors 总被引:1,自引:0,他引:1
Tobacco genetic tumors developed spontaneously from hybrid plantsthat are derived from sexual or somatic crosses between twospecies of Nicotiana. Thus, genomic transformation by T-DNA,as occurs in cases of crown galls and hairy roots, is not indispensablefor the initiation of such genetic tumors. Tumorization may be attributable to expression of certain genomicgenes that are highly homologous to those of the T-DNA of Ri-plasmids,with subsequent overproduction of phytohor-mones and/or to elevationin sensitivity to endogenously supplied phytohormdnes of cellsof the hybrids. Tumorization events occur sequentially afterstimulation by stress, such as wounding. (Received August 19, 1991; ) 相似文献
2.
S Kato S Itoh Y Miura H Naito T Noguchi 《Comparative biochemistry and physiology. B, Comparative biochemistry》1990,97(4):783-791
1. We have characterized the insulin receptor in primary cultured quail oviduct cells and examined the hormonal regulation of its level. 2. We have also shown the recycling pathway of insulin receptors in the cultured cells using specific inhibitors (tunicamycin, chloroquine, monensin, and brefeldin A). 3. Our data suggest that glucocorticoids play important physiological roles in egg-white protein synthesis through increasing the number of insulin receptors and insulin through enhancing the transport of amino acids. 相似文献
3.
4.
Yuji Inaba Yoshio Tanaka Sukemitsu Ishii Tomiaki Morimoto Kunihiko Sato Tuneyoshi Omori Minoru Matumoto 《Microbiology and immunology》1970,14(5):351-360
Replication of Ibaraki virus was not inhibited by 5-iodo-2′-deoxyuridine, indicating that the virus is an RNA virus. The virus was resistant to ether, chloroform and deoxycholate, sensitive to trypsin, very labile at acidic pH but stable at pH 6.4 or higher, and was resistant to repeated freezing and thawing. The virus was readily inactivated at 56 C or higher, was fairly stable at 37 C, and very stable at 4 C, while it rapidly lost infectivity when stored frozen at —20 C. The virus was readily sedimented by centrifugation at 40 000Xg for 60 min. It readily passed through membrane filters of 200 mμ pore size, passed through 100 μfilters but only with some titer loss and did not through 50 mμ filters. In these tests, the bluetongue virus used as a control behaved in the same manner as Ibaraki virus. These findings provide additional evidence for the similarity of Ibaraki virus to bluetongue virus which had been previously demonstrated on the basis of seasonal incidence, symptomatology and pathology of the diseases caused by these viruses and the behavior of the viruses in cell cultures, embryonated eggs and laboratory animals. The present study, however, provided no evidence for any serological relation between these two viruses. More Information is needed to reach a final decision on the classification of Ibaraki virus, particularly regarding the morphology of the virion, the doublestrandedness of the viral RNA and other basic features. 相似文献
5.
6.
7.
The R-form lipopolysaccharide (LPS) from Klebsiella strain LEN-111 (O3-:K1-) forms a hexagonal lattice structure with a lattice constant of 14 to 15 nm when it is precipitated by addition of two volumes of 10 mM MgCl2-ethanol. When the LPS was suspended in various buffers (50 mM) at pH 2 to 12 for 24 hr at 4 C, at pH 2 and 3 pits of the hexagonal lattice structure markedly disappeared, at pH 4 to 8.5 the lattice structure was stable, and at pH 9 to 12 it tended to loosen somewhat. The LPS from which cations were removed by electrodialysis retained the ability of hexagonal assembly, although the lattice constant of the hexagonal lattice of the electrodialyzed LPS was large. The lattice structure of the electrodialyzed LPS was much more labile than that of the non-electrodialyzed LPS at alkaline pH levels and the former was completely disintegrated into ribbon-like structures when the LPS was suspended in 50 mM Tris buffer at pH 7.7 or higher. However, the electrodialyzed LPS formed a hexagonal lattice structure in Tris buffer at pH 8.5 containing 0.1 to 100 mM MgCl2. The lattice constants of the hexagonal lattice formed by the electrodialyzed LPS at 10 or 100 mM MgCl2 were very similar to that of the lattice of the non-electrodialyzed LPS. From these results it is concluded that the lability of the hexagonal lattice structure of the electrodialyzed LPS at alkaline conditions is due to removal of Mg2+ by electrodialysis. 相似文献
8.
Hiroyuki Kozu Isao Kobayashi Mitsutoshi Nakajima Kunihiko Uemura Seigo Sato Sosaku Ichikawa 《Food biophysics》2010,5(4):330-336
This paper uses computational fluid dynamics to simulate and analyze intragastric fluid motions induced by human peristalsis.
We created a two-dimensional computational domain of the distal stomach where peristalsis occurs. The motion of the gastric
walls induced by an antral contraction wave (ACW) on the wall of the computational domain was well simulated using a function
defined in this study. Retropulsive flow caused by ACW was observed near the occluded region, reaching its highest velocity
of approximately 12 mm/s in the narrowest region. The viscosity of the model gastric contents applied in this study hardly
affected the highest velocity, but greatly affected the velocity profile in the computational domain. The shear rate due to
gastric fluid motion was calculated using the numerical output data. The shear rate reached relatively high values of approximately
20 s−1 in the most occluded region. The shear rate profile was almost independent of the fluid viscosity. We also simulated mass
transfer of a gastric digestive enzyme (pepsin) in model gastric content when peristalsis occurs on the gastric walls. The
visualized simulation results suggest that gastric peristalsis is capable of efficiently mixing pepsin secreted from the gastric
walls with an intragastric fluid. 相似文献
9.
10.
N Kato I Nakashima M Ohta F Nagase T Yokochi S Naito 《Microbiology and immunology》1980,24(11):1043-1051
The time course of development and decline of the ability of BCG-infected mice to produce interferon in the serum in response to the intravenous infection of purified protein derivative of tuberculin (PPD) was very similar to that of their systemic hypersensitivity to PPD. A cytotoxic factor (cytotoxin) was produced in parallel with interferon in the serum of BCG-infected mice after stimulation with PPD. The duration of the period in which cytotoxin-production responsiveness to PPD was definitely detectable was much shorter than that for interferon-production responsiveness although the periods for the maximum production of interferon and cytotoxin coincided. The kinetics of release of interferon in the serum of BCG-infected mice after stimulation with PPD did not parallel that of release of cytotoxin. The four kinds of activities, interferons and cytotoxins induced by PPD and lipopolysaccharide (LPS) in the serum of BCG-infected mice, were compared for their stability to heating at 56 C and to treatment at pH 2. The kinetics of inactivation of these four activities differed significantly, when the serum was either heated at 56 C or treated at pH 2. Interferon produced in response to LPS could be neutralized by anti-L cell(NDV) interferon rabbit serum as easily as L cell (NDV) interferon, 16 times as much antiserum was required to neutralize the same amount of interferon in response to PPD, but cytotoxins induced by PPD and LPS were not neutralized at all by the antiserum. From these findings it is thought likely that interferons and cytotoxins induced by PPD and LPS in the serum of BCG-infected mice are different substances, although the antigenic relationship between cytotoxins induced by PPD and LPS remains unknown. 相似文献